The present invention relates to a gap detector for detecting a gap between a liquid ejecting head and a target medium by detecting a rotating state of a carriage guide shaft.
The present invention also relates to a liquid ejecting apparatus incorporating such a gap detector and to a gap detecting method executed in such a liquid ejecting apparatus.
The liquid ejecting apparatus is not limited to a recording apparatus, such as a printer, a copier, or a facsimile, which employs an ink jet recording head and ejects ink from the recording head to a recording medium, to thus effect recording. The liquid ejecting apparatus is employed to encompasses an apparatus that ejects a liquid appropriate to an application, in place of ink from a liquid ejecting head corresponding to the ink jet recording head onto a target medium corresponding to a recording medium, thereby causing the liquid to adhere to the medium.
In addition to the recording head, the liquid ejecting head encompasses a coloring material ejecting head used for manufacturing a color filer such as a liquid-crystal display or the like; an electrode material (conductive paste) ejecting head used for forming electrodes, such as an organic EL display or a field emission display (FED) or the like; a bio-organic substance ejecting head used for manufacturing a bio-chip; a sample ejecting head serving as a precision pipette; and the like.
Some of the liquid ejecting apparatus are configured to be able to adjust a gap between a liquid ejecting head and a target medium or a platen for supporting the target medium (hereinafter abbreviated as “the platen gap”), as described in Japanese Patent Publication No. 2002-67428A, in order to appropriately perform recording (liquid ejection) on a variety of types of target media (recording media); more specifically, recording media of different thicknesses.
In the recording apparatus disclosed in the above publication, a carriage guide shaft is formed into an eccentric shaft structure, so that the carriage is vertically actuated in association with rotation of the carriage guide shaft, to thus control the platen gap. Further, the control of the platen gap is not manually performed but automatically controlled by rotating the carriage guide shaft with a driving force of a motor.
With this configuration, several positions for defining different platen gaps can be determined. For instance, there may be a case where four positions are set; namely, a position for recording information on plain paper, a position for recording information on a cardboard, a position for recording data on an optical disk, and a position where a tray having an optical disk set thereon is inserted. In order to achieve a superior recording result, appropriate print control must be performed for each position.
Accordingly, when recording is carried out, a control section of a printer must recognize the current platen gap. To this end, a detector for detecting the current platen gap is required. Japanese Patent Publication Nos. 2003-211778A and 2004-314591A disclose a technique for detecting the current platen gap. For instance, Japanese Patent Publication No. 2003-211778A discloses a device capable of identifying four positions by a combination of activation/deactivation of two sensors. Japanese Patent Publication No. 2004-314591A discloses a stable area sensor. In this sensor, a disc, which has four light-shielding plates provided around an outer periphery thereof, is attached to a carrier guide shaft, to thus detect a light-shielding plate that is now blocking the optical sensor. Since each of the light-shielding plates corresponds to one of the platen gaps, the current platen gap can be determined based on the detection result.
However, the above technique requires a plurality of exclusive sensors for detecting a plurality of platen gaps, which has become a factor for incurring a cost hike.
This technique also raises the following problem. Provision of an exclusive motor for switching the platen gap entails a cost hike. Accordingly, the recording apparatus is desirably constructed to cause the motor that drives a roller for transporting a recording medium to double as a motor for switching the platen gap; and to transmit or cut off power from the motor to the carriage guide shaft, as required. Here, operation for switching transmission and cut-off of power from the motor to the carriage guide shaft can also be performed by a carriage. Specifically, the recording apparatus is provided with an actuated member and the actuated member is pressed by the carriage, to thus switch transmission of power from the motor to the carriage guide shaft.
With this configuration, the number of components can be curtailed, which is preferable in terms of cost. However, the construction raises the following problem. Specifically, when a recording sheet is present in a position where a carriage opposes a recording head during the course of the carriage proceeding to press the actuated member, the recording head may rub against the recording sheet when switching to the platen gap appropriate to the recording sheet has not yet been performed, or the recording head may collide with a side edge of the recording sheet, to thus cause paper jamming. When a tray having a plate-shaped member, such as an optical disk, set therein is inserted into a transporting path while sufficiently-large the platen gap is not ensured, the tray collides with a recording head in the same manner, which in turn may induce a failure. If a distance, over which the carriage travels, is long when the carriage proceeds to press the actuated member, operation for switching the platen gap requires consumption of much time.